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Monday, 09 June 2008


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Thanks for that, Carl (and Mike). Clear and useful, well illustrated. As usual.

I'm beginning to think that I might have made a mistake by returning the K20D to B&H and getting a Canon XSi instead.

Carl, many people on forums are reporting a big increase in AF performance with respect to the K10D. And what did Pentax say? Nothing. Well, actually, I believe they stated that the K20D had the same AF as the K10D. So which is it? I cannot believe so many people who have both the K10D and K20D can be wrong about the improved AF, but if it *is* better, then Pentax must have improved it somehow.

Or maybe, we're witnessing the first case of natural selection in the technological wild. I random binary mutation has improved the K20D's AF, which will result in an improved ability to procreate and produce faster focusing offspring.

OK, so I need to iron out some details of my theory...

Carl, 1/40 at f/4 and ISO800 doesn't sound all that dark. How about 1/10 @ f/2.8 and ISO 800? Is everything still working crisply?


I'm mildly curious about this, since I actually sold my K10D about six months ago because of the slow AF in low light. Unfortunately, it was also slow with the Limited primes (43 & 77 in particular, less so with the 21, 31 & 70) even in good light. Since those primes were the main reason I chose a Pentax DSLR, it didn't make sense to stick with the system.

I've missed those lenses, however, and if the K20D AF really is closer to Canon and Nikon's AF I'd be interested. Very interested.

from above (scott) "Carl, 1/40 at f/4 and ISO800 doesn't sound all that dark."

my sentiments exactly. on top of which, you have high contrast subjects (good af targets) under spot lighting. while the contrasty light is obviously challenging for exposure, it is the opposite of challenging for af.

i routinely shoot in much, much lower light (more like iso1600, f/1.4, 1/25sec). my camera system often focusses even in light that low, provided i can point it at a contrasty target (which i can't always). moreover, i could focus an f3 and a leica rf in light that low or lower reliably and quickly. it seems disingenuous to me to compare your situation to those systems here.

i wish you the best with the pentax. it has features i'd like on my camera, and generally seems like a great kit. obviously, it suits you. but i'm still waiting to see an evaluation of af in challenging conditions.


Given the relative rarity of fast (like the old days with film cameras) lenses today and the relatively good quality of results at ISO 800, plus the usefulness of various anti-shake systems, I agree that 1/10th @ f/2.8, ISO 800 is an interesting test point.

I just located a situation around the house that met these conditions and shot some tests with the 35mm f/2.8 macro from a distance of eight or ten feet. Focus was slower, consistently taking about half a second to settle. The shots were correctly focused on the target point. I'll be interested to compare that performance to competitive equipment.

I upgraded from a K10D to the K20D. And indeed the autofocus seems like it was redesigned completely.

From what I've read, it seems the early K10D units were plagued with AF issues. Pentax fixed the problem in later units. So if you bought a K10D in the latter part of its production run, you're not supposed to see an improvement in autofocus performance between the K10D and K20D.

Those of us who bought the K10D early on do however see a huge improvement. So much so that I won't use my K10D anymore.

Thanks for your work, Carl. Always a pleasure reading the site

I had some issues with my late K10D, but low light for me was 1/8 second at ISO1600 and f2.8

Now I'm shooting at 1/8-1/15 at ISO 6400 and f3.5-f4 on my D300 and AF is much better.

As to the K10D/K20D AF differences, they share an AF system, but not necessarily AF firmware. Likely all updates were in the firmware. There's likely a lot more performance to be found in the AF unit given its similarities to Nikon's Multi-CAM2000 unit from the D2's and F6, which is very similar from a hardware point of view, but much higher performance.

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